President Donald Trump claimed on Monday he had "somewhat compromising" information on an unidentified Democratic senator as he eviscerated the party for its handling of Brett Kavanaugh's Supreme Court nomination.

Trump exploded on Senate Judiciary Committee Democrats, alleging moral hypocrisy and unfair treatment of the appeals judge after a sexual assault accusation. Without naming the senator or providing any evidence, Trump suggested he had damaging information about a Democrat, whom he called "pretty aggressive."

Asked later who the senator is, Trump declined to name the lawmaker and said he would "save it for a book like everyone else." The president has a long history of making unfounded claims, then failing to provide evidence to back those assertions. The Supreme Court's term began Monday with only eight justices. Ford, who gave emotional testimony before the Judiciary Committee last week, has said she had no political motivation in coming forward and felt it was her "civic duty."

Kavanaugh angrily denied the accusations last week and had tense interactions with several Democrats on the Judiciary Committee. Facing requests from several key senators to delay a vote on Kavanaugh's confirmation, Trump asked the FBI on Friday to open a supplementary background investigation into Kavanaugh amid Ford's accusation and two other sexual misconduct claims.

In rambling comments Monday, Trump mentioned some lawmakers by name as he claimed "bad reports" existed about everybody.

He pointed to Sen. Richard Blumenthal, D-Conn., who the president said "lied about Vietnam" and his supposed service in the war there. In 2010, Blumenthal apologized for misleading voters into thinking he had served in Vietnam, when he was actually in the Marine Reserves and was never deployed.

"Here's a guy that lied and now he's up there talking like he's holier than thou," the president said.

Trump also claimed Sen. Cory Booker, D-N.J., "ran Newark, New Jersey into the ground" and was a "horrible mayor" of the city. Conservatives have latched on to a column Booker wrote while at Stanford University, in which he admitted to "groping" a friend. He said the experience informed his understanding of sexual consent and his efforts to advocate for assault survivors.

"And now he's talking about Judge Kavanaugh! And I could go through a whole list of them, OK?" Trump said.

He also criticized the committee's top Democrat, Sen. Dianne Feinstein of California, for keeping Ford's accusation private for weeks after she received a letter about it. The senator said she kept the information confidential, as requested by Ford in the letter.

Later, The Intercept reported on the existence of the letter, and Ford eventually came forward publicly in The Washington Post. Both Feinstein and the news outlet have denied that the senator's office leaked the letter.

"She didn't have to wait until after [Kavanaugh's confirmation hearing] was closed, essentially. She should have said listen, I have a problem," Trump said.

Spokespeople for Blumenthal, Booker and Feinstein did not immediately respond to CNBC's requests to comment.